MRAC LOAD TORQUE OBSERVER FOR POSITION CONTROL OF A BRUSHLESS DC MOTOR

A new control method for the robust position control of a brushless DC (BLDC) motor using the adaptive load torque observer is presented. Fo r a BLDC motor system, approximately linearized using the held-orienta tion method, it is shown that the augmented state variable feedback ca n be applicable to this system. To overcome the problem of the unknown parameter, or of parameter variation such as a flux linkage, a model following adaptive control mechanism is employed for the load torque o bserver. Stability analysis is carried out using the Lyapunov stabilit y theorem. As a result, the robustness can be obtained without affecti ng the overall system response. The load disturbance detected by the a daptive O-observer is compensated for by feedforwarding the equivalent current having the fast response.